Carburetors



.une 26, 1956 G. J. GRETZ CARBURETORS Filed Dec. 17, 1952 22a 19a 9 Q2Fig.

United States Patent .CARBURETGRS VGeorge LGretLPittsburgh, Pa.

Application December 17, 1952, Serial No. 326,495

4 Claims. (Cl..261-'-23) My invention relates to carburetors, andyparticularly to down draft carhuretors of the plain tubetype.

It is well -known that the present day plain tube types tof Vdown draftcarburetors in Vcommon use provide a compromise -between the best Vwideopen throttle power at 'slow speeds and Athefhighest speed under levelroad driving conditions, economy Vand maximum power being sacrificed forspeed.

'One object of my present invention is to provide an improved down.draft carburetor ofthe plain tube type providing better performancezatall speeds without saericing economy in full consumption.

Another object of my invention is .to provide a down draftcarburetor ofthe type described in .which there is no -after drip when the-.caron'which it isinstalled is brought to a sudden-stop or isstopped onagrade.

Another object .of .my invention-is .to provide an improved carburetorof the type described which will furnish a longer Yrange of ,smoothervoff idle performance without any so-called flat spots.

Another object of my inventionis to provide acarburetor of the typedescribed having .a constant and more uniform 'distribution of fuel atall engine speeds or throttle positions.

Another object of my invention is to provide 'a carburetor of the typedescribed -having -two separate Venturi openings, one of which becomeseffective ,to'provide additional fuel'mixture in response to high enginevelocity when the throttle is open.

A further object of myv invention is to V.provide acarburetor in whichthe Venturi `.openings are in removable sleeves and-in which thegoriiices which 'discharge fuel vinto the Venturi passages areinaremovablemember, whereby .by substituting different sleeves -anddilerenti members the Ydisposed respectively inmain-,and ,auxiliaryVenturi openings. The oat chamber which'is formed aspart of the centralbody section is semi-circular and has .its ycenter located atsubstantially the verticaljportions of thefuel channels. The fuel `levelvis 4maintained k,no zhigher `than the upper -ends :of the verticalportions of `the fuel .channels 'and as a Vresult fuel'will not .run outor drip .when

V the car is brought toa sudden stop V,or stopped :on a

grade.

The fuel mixture .at ,idlingspeeds is supplied through alow speedcircuit comprising .a first vertical vvpassageway Vwhich communicates atits upper ,'en'd with the horizontalportionrof the main fuel channel.and at its lower .end with arst discharge port containing the idlingadjustment screw. A branch-passageway connects this yfirst`verticalpassageway with Va second port-which'is so lo- 2,752,13Patented .Jurre l26, 1956 ICC cated with respect to the throttle `thatwhen the throttle is closed no fuel is discharged through this port, butas the throttle opens the second portis gradually opened to the airstream to cause it to discharge fuel into the air stream in parallelwith the first port, this second port being effective Ato provide theproper fuel mixture for speeds between idling speeds and a predeterminedlow yspeed such for example as 22 miles per hour. VIt should be notedthat at closed throttle the main discharge port and the second portmeter air into the low speed idling system.

The low speed idling system also includes a `second vertical passagewaycommunicating at its upper end with the horizontal portion of the mainfuel channel and at its lower end with a third discharge port disposedabove Vthe second port. An airbleed passageway connects both verticalpassageways between theepoint of connection with the horizontal portionof the main fuel channel directly with the main discharge port. As thethrottle is gradually-opened the second port is gradually transformedfrom an air bleed port to a fuel discharge port, and as the suctioncontinues to increase the third discharge port starts to dischargeadditional fuel into the air stream. This continues to a predeterminedspeed such, for example, as 45 milesrper hour under level road drivingconditions. As the throttle continues to open, the main discharge portis gradually transformed from an air bleed into a fuel discharge port.

The carburetor also includes .a second Venturi opening in parallel withthe Inain Venturi opening. This second `opening isnormally closed at`its'lower end by a buttery valve biasedto its closed position by aspiral spring connected to the accelerator pump operating link in such,manner that as the throttle is opened the spring tension is graduallydecreased. A'portion of this butterfly valve extends into the main airstrearnso that as the velocity of the air suction increases, it willproduce an increasing force tending to open .this valve. Fuel is,supplied to this lsecond Venturi opening by an auxiliary discharge portconnected to the horizontal portion of the auxiliary fuel channel. Theparts `are so `proportioned that at the higher engine speeds, such, forexample, as 6() or more miles per hour-under level road drivingconditions, -if `the throttle is open so Vthatthe tension on the ispringbiasing the butterfly valve :to its closed position is reduced, thisvalve will open Yand will thus cause the aux- Viliary -discharge port todischarge fuel into the second Venturi opening. This Yauxiliary Venturiopening enables the main Venturi opening Vto be reduced ,in size andthus obtain -betterfuel economy at the usual driving ,speeds and alsobetterpower at slow speed wide open throttle conditions, withoutsacrificing vacceleration or power at the higher driving speeds.

My .carburetor further includes va novel buffer mecharusm forYcontrolling .the movement .of the .throttle to its -fully closedposition when the throttle is suddenly Vreleased to enable vthe .car tobe brought to .a sudden stop without stalling the motor. This buffermechanism is so constructed that it will regulate the rate of closing ofVthe throttle in thelastfew degrees ofits movement to its closedposition .to a .Value which will prevent stalling.

Other objectsand characteristic features of my invention will becomeapparent Vas the .description proceeds. I `shall .describe one lform of.carburetor embodying my invention, and shall then point out .the novel.fea-

tures thereof in claims.

In the accompanying drawings, Fig. 1 is a side elevational view of acarburetor embodying my invention with .a l portion broken away and `insection to show the Aaccelerating pump.

tFig. V2 Vis a Ysectional'view taken on the line Ill-II of Fig. `l.

Fig. 3 is a sectional view taken on the line III-III of Fig. 2.

Fig. 4 is a sectional View taken on the line IV-IV of Fig. 2.

Figs. 5 and 6 are detail vertical sectional views of the Venturi tubesand 11 forming part of the carburetor shown in Figs. 1, 2 and 3.

Fig. 7 is a detail vertical sectional view of a member 24 which housesthe main and auxiliary fuel channels for the carburetor shown in Figs.l, 2 and 3.

Fig. 8 is a vertical sectional view of a modified arrangement of theVenturi tubes and member 24 for the carburetor shown'in Figs. 1, 2 and3.

Fig. 9 is a detail sectional View taken on the line IV-IV of Fig. 2.

Similar reference characters refer to similar parts in each of theseveral views.

Referring now to the drawings, the carburetor in the form here showncomprises three sections 1, 2 and 3 separated by suitable gaskets 4 and5 and bolted together in the usual manner by bolts 6 and 7. The varioussections may be constructed in any suitable manner, but will usuallyconsist of die castings as is customary.

The upper section 1 contains the air inlet 8 which is divided by apartition 9 into two separate passageways 8a and 8b leading into mainand auxiliary Venturi openings lta and 11a formed in Venturi sleeves 10and 11 disposed in the main body portion 2 of the carburetor. The uppersection 1 also houses a choke valve'12 so disposed that when it is movedto its closed position it will close or restrict the passageway 8a.

The Venturi openings '10a and 11a communicat through passageways 13a and13b with the induction passage 14 of the carburetor. The inductionpassage 14 is located in the lower or throttle body 3 of the carburetor,and cooperates with a throttle valve 15 mounted on a throttle valveshaft 16 journaled in the throttle body 3.

As will appear 'more fully hereinafter, fuel is at times discharged intothe main Venturi opening 10a at the throat of the opening through maindischarge ports 17 which communicate with a fuel well 18 through a mainfuel channel 19 and a main fuel metering jet 20, while fuel is at timesdischarged into the auxiliary Venturi opening 11a at the .throat of theopening through auxiliary discharge ports 21 which communicate with thefuel well 18 through an auxiliary fuel channel 22 and an auxiliarymetering jet 23. VThe fuel channels 19 and 22 are disposed in atransversely extending member 24 which tits with a snug t into suitableopenings formed in the upper part of the main body portion 2 in suchmanner that this member can be readily removed to enable the fuelmetering jets to be cleaned, or removed and replaced with jets ofdilferent sizes to permit the carburetor to be readily adapted todifferent engines having different fuel requirements.

The Venturi sleeves 11 and 12 are also readily movable so that thesesleeves can be changed to adapt the carburetor to different enginerequirements, and these sleeves and the transverse member 24 may eitherbe made in separate parts, as shown in Figs. 5, 6 and 7, or they may allbe made in one piece as shown in Fig. 8, since cach different size ofVenturi opening will ordinarily require a dierent size jet.

The fuel well 18 communicates through passageways 25 and 26 with a fuelbarrel or float chamber 27 provided with atfuel inlet valve 28'and afloat mechanism 29 for controlling the flow of fuel into the floatchamber 27. The float chamber 27 is formed as part of the central bodysection 2 and has its center located as close as Vpossible to thevertical portions 19b and 22b of the fuel channels 19 and 22, that is atthe center of the fuel well 18.V The float mechanism is adjusted tomaintain the -fuel level no higher, and preferably slightly lower, thanthe upper ends of the Vertical portions 19h and 22b of 4 the fuelchannels, and as a result since the center of the fuel in the fuel wellis located substantially at the center of the fuel in the oat chamber,fuel will not run out of the main and auxiliary fuel discharge portswhen the engine is at rest regardless of the angle at which thecarburetor is tilted. Likewise, fuel will not run out or drip when thecar is brought to a sudden stop or is stopped on a grade.

The fuel mixture at idling and low speeds is supplied through a lowspeed circuit comprising a first vertical passageway 3G whichcommunicates at its upper end with the horizontal portion 19a of themain fuel channel 19, and at its lower end with a low speed dischargeport 31 provided with an idling adjusting screw 32. A branch passageway30a connects this first vertical passageway 36 with a second dischargeport 33 which is so located with respect to the throttle valve that whenthe throttle valve is closed no fuel will be discharged through thisport, and this port will function as an air bleed because it is abovethe throttle valve. However, as the throttle valve is opened, thissecond port is gradually exposed to the air stream in parallel with theport 31. It should be pointed out that when the throttle valve isclosed, air is sucked in through the main discharge ports 17 into thehorizontal portion 19a of the main fuel channel where it mixes with fuelsucked through the vertical portion 19b of the main fuel channel 19. Theemulsion thus Vformed is sucked down through the passageway 30 anddischarged into the induction passage 14 through the low speed dischargeport 31. The idling adjusting screw is adjusted to give the desiredidling speed of the engine. As the second port 33 becomes exposed to theair stream fuel is also discharged into the air stream through this portin parallel with the port 31, this second port being effective toprovide the proper fuel mixture for speeds between idling speed and apredetermined low speed such, for example, as 22 miles per hour.

The low speed idling system also includes a second vertical passageway34 communicating at its upper end with the horizontal portion 19a of themain fuel channel 19 and at its lower end with a third discharge port35' opening into the induction passage 14 above the second port 33. Anair bleed passageway 35a connects both Vertical passageways 30 and 34 ofthe low speed system intermediate their ends directly with the maindischarge ports 17. As the throttle is opened wider the second port 33is gradually transformed from an air bleed port to a fuel dischargeport, and as the suction continues to increase the third port 35 startsto discharge additional fuel into the air stream. This action continuesto a predetermined speed such, for example, as 45 miles per hour underlevel road driving conditions. At still higher speeds, the maindischarge ports 17 are gradually transformed from an air bleed into fueldischarge ports.

The carburetor includes an accelerating pump P located at one side ofthecentral body portion 2. The accelerating pump is connected to theshaft of the throttle valve vin a manner which will be made clearpresently, and is effective at each sudden opening of the throttle valveto discharge a jet of fuel into the main Venturi opening 10a.

The pump P is provided with two concentrically arranged plungers 42-and43 respectively mounted ina cylinder A47 formed in the main body portion2. The cylinder 47 terminates at its lower end in a concentric cylinder48,

having a diameterwhich is just large enough to receive Y the mainplunger 42,-and the cylinder 48, in turn, is connected through apassageway 49 and a check valve 50 with the oat chamber 27. It will beobvious that each time the plungers are moved to their upper positions,as shown,

the cylinders 47 and 48 will both fillup with gasoline.

arreglar .of the rod 57 is 'connected' by means of a link '59toatsegment 60 secured to the shaft 16 whichactuates the throttle valve.

The auxiliary plunger A3 surrounds and slides on the -main plunger 42,and is provided at-its upper-end with an inwardly extending annularflange v45 which tits theplunger rod 44 with a sliding t. A vcoil spring48 surrounds the plunger rod 144 between vthe plunger 43 and the ,crossmem- -ber 56 and biases-theauxiliary plunger to the position in whichthe ange 45 engages the top of thevmain plunger. This spring actswhenlthe-throttle-valve-is opened to maintain the two plungers ,42and'43to the'relative positions shown.

Upo-n up strokes ofthe pump caused Yby closing of the throttle, fuel owsinto the cylinders 47 and 48 ,from the oat chamber 27 through the checkvalve 50 and passageway 49, while uponeach quick down stroke of the mainplunger 42 which occurs each time the throttle valve is opened quickly,fuel is discharged by the main plunger through a duct or channel 46 toan outlet orifice or jet 53 disposed in the main Venturi opening a. Theduct or channel .46 is provided .with a non-return valve more or lessdiagrammatically shownat 54. The main plunger 42 is provided-with alongitudinally extending groove 5S which is slightly longer than thecylinder 48. This groove has a two fold purpose. 'When the throttlevalve is opened slowly, the main plunger .42 will move down slowly andwhile some fuel will be expelled from jet 53, part of the fuel in thecylinder y49 will pass up through this groove V55 into cylinder47 fromwhichit .will later be expelled by the supplementalplunger 43 throughsaid groove and through jet-5,3 by .way of. duct or;passage .46.

Upon a quickdownwardV movement of the main plunger which occurs uponeachvquick opening of the throttle, a larger amount oftfuel will bedischarged-through jet 53 by the main plunger than would Vbe dischargedon a slow opening of the throttle and the fuel trapped in cylinder 46below piston 43 will belgradually-expelled Vfrom this cylinder by way ofgroove S5 and duct 53. The supplemental piston acts as a follow uppiston and prolongs the period during which the accelerating dischargetakes place.

VIt will be seen, therefore, that the accelerating `pump operates insynchronism with the-throttle valve and-functions so as to provide asupply of accelerating fuel at the times and in the amounts needed.

The auxiliary Venturi opening 11a is provided for the purpose ofproviding a richer fuel mixture at the higher engine speeds to providegood high speed performance without sacricingfuel economy at the lowerengine speeds. The passageway 13b which connects the air inlet 8 withthe induction passage 14 through the auxiliary Venturi opening 11a isnormally closed at its lower end by a buttery valve 61 mounted on ahorizontal shaft 62 journaled in the main body portion 2 of thecarburetor. The shaft 62 projects out through the sidewall of the mainbody portion 2, and is provided at its outer end with a spiral spring63, one end of which is secured to the shaft 62 and the other end ofwhich is secured to the link 59 which actuates the accelerator pump insuch manner that the valve is biased to its closed position by a forcewhich will decrease as the throttle valve is opened. The buttery valve61 is made somewhat wider than the lower end of the passageway 13b toprovide a portion 61a which projects into the passageway 13a where it issubjected to the velocity of the air stream passing through thepassageway 13a. The parts are so proportioned that at the lower enginespeeds the biasing force exerted by the spring 63 will maintain thevalve 61 closed. However, at the higher engine speeds, such for example,as 60 or more miles per hour under level road driving conditions, if thethrottle is opened far enough so that the tension exerted by the Fspring 63 is reduced, the velocity of the air stream acting on theportion 61a of the valve will exert a force on the valve which issuicient to open it, and the auxiliary discharge ports 21 then becomeeffective to discharge additional fuel into the Venturi opening 11a andhence with positions.

.the bore 66 below the piston 65.

the'induction passage 14, thus providing aricher yfuel mix- -turetogivegood engine performance atthe higher lengine speeds.

The ycarburetor further includes means-for controlling the Ymovement ofthe throttle toits fully vclosed position when the accelerator pedal issuddenly released to .enable -the car to be brought to a suddenstopiwithout stalling :the motor. 65 slidably mounted in a bore 66connected bya-passage- .way 67 with the oat chamber 27. The piston 65.is

As here shown, this means comprises afpiston formed on the lower end ofa piston rod 68, the upper fend of which is connected by arm 69 to a.verticalfactu- .ating rod '7G slidably supported in a guideway 71. The-rod 76 is operatively connected at its lower ,end lto the `throttle.valve shaft i6 by a lost motion connection including a Y'tl-shaped link72 pivotally attached atone yside to the lower end of the'rod 70 andslidably mounted at the other side in an arcuate slot 73a formed in aseg- .ment .73 secured to the .throttle valve'shaft 16. The piston iscounterbored at 65a to slidably receiveaplunger 74 secured at its lowerend to the valve body 2. The

.plunger .74 is provided with a vertical passageway 75 which isconnected at its lower end with the passageway respect to the plunger74.

As shown in Fig. 4, the ports are in their closed throttle As thethrottle is opened, the resulting movement of :the segment 73 removesany downward 'force frorn the lower end of the rod 70 and hence from theypiston rod 6S,.antl as a result the spring 77 which is under.compression in theclosed throttle position forces `the piston .65.upwardly and causes gasoline to be sucked into 'I'he spring is soproportioned that if the throttle is opened far enough it will .forcethe piston 65 upwardly to a position in which .the

plunger 7.4 is completely withdrawn from vthe counterbore Y65apermitting the bore 65u to become completely `filled .with gasoline.`the throttle is fullyopened the piston y65 will be moved :tto-the upperend of the cylinder by engagement ofthe The slot 73a is so proportionedthat .when

link 72 with the right-hand end of the slot 73a as viewed in Fig. 4.When, however, the throttle is permitted to close, the slot 73a permitsthe throttle to close quickly until the throttle is approximatelytwo-thirds closed whereupon the link 72 will then engage the left-handend of the slot 73a, as viewed in Fig. 4, and cause the piston 65 tomove downwardly to a position in which the plunger 74 starts to enterthe counterbore 65a. When this happens the gasoline which is thenpresent in the bore 66 is expelled at a rate which depends upon the sizeof the opening 76 and this opening is made suiciently small to regulatethe rate of closing of the throttle in its last few degrees of movementtoward its closed position to a value which will prevent stalling.

One advantage of a carburetor embodying my invention is that since foreach throttle opening or closing all air bleed ports serve also as fuelports there is no clogging -of the ports by carbon, whereby one of thecommon troubles of present day carburetor is eliminated.

Another advantage of a carburetor embodying my invention is that it issimple in construction and therefore economical to manufacture.

Another advantage of a carburetor embodying my invention is that itprovides good performance under all operating conditions and at the sametime provides good fuel economy.

Although l have herein shown and described only one form of carburetorembodying my invention, it is understood that various changes andmodifications may be vmade therein YWithin the scope of the appendedclaims without departing from the spirit and scope of my invention.

`Having thus described my invention, what I claim is: 1. In a carburetorhaving a single air inlet connected through main and auxiliary venturiopenings with a single induction passage, main and auxiliary fueldischarge ports disposed in said main and auxiliary venturi Vopeningsrespectively, a single throttle valve disposed in said inductionpassage, a second valve having a closed position in which it preventsthe ow of air through said auxiliary venturi opening and an openposition in which it permits the flow of air vthrough said auxiliaryventuri opening, said second valve being biased to a closed position bya force which is responsive to the throttle valve position and whichdecreases as the throttle valve is opened and having a portion whichprojects into the air Vstream passing through said main venturi openingfor opening said second valve when the velocity of the air passingthrough said main venturi opening exceeds a predetermined velocity.

2. In a carburetor having a single air inlet connected through main andauxiliary venturi openings with a single induction passage, main andauxiliary fuel discharge ports disposed in said main and auxiliaryventuri openings respectively, a single throttle valve disposed in saidinduction passage, a second valve having a closed position in which itprevents the ilow of air through said auxiliary venturi opening and anopen position in which it permits the flow of air through said auxiliaryventuri opening, said second valve being biased to a closed position bya force which is responsive to the throttle valve position and whichdecreases as the throttle valve is opened and having a portion whichprojects into the air stream passing through said main venturi openingfor opening said second valve when the throttle Vis opened more than apredetermined amount and the velocity of the air passing through saidmain venturi opening exceeds a predetermined velocity.

3. In a carburetor having a single air inlet and a single inductionpassage connected through main and auxiliary venturi openings, means fordischarging fuel into said venturi openings to provide a fuel mixture, athrottle valve in said induction passage, and a second valve disposed atthe lower end of said auxiliary venturi opening f8 and normally biasedto a closed position by a spring connected to said throttle valve, saidsecond valve having a portion extending into the air stream throughsaid'main venturi opening for opening said second valve to provideadditional fuel mixture in response to high engine velocity when thethrottle is open.

4. In a carburetor having a single air inlet and a single inductionpassage connected through main and auxiliary venturi openings, means fordischarging metered amounts of fuel into said venturi openingsinproportion to the velocity of the air stream passing therethrough, athrottle valve in said induction passage, and means responsive to thethrottle valve position for preventing the passage of air through saidauxiliary venturi opening except when said throttle valve is opened morethan a predetermined amount and the velocity of the air stream exceeds apredetermined velocity, said means comprising a buttery valve effectivewhen closed to prevent the flow of air through said auxiliary venturiopening and biased to its closed position by a force which decreases asthe throttle valve is opened and having a portionV projecting into theair stream through said main venturi opening in such manner that the airstream in said main venturi opening will exert a force on said butterflyvalve in opposition to said biasing force tending to open said butteryvalve.

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